Mad Professor's Simble Predriver is not just a preamp, but a preamp/booster/compressor/upper harmonic enhancer.This musical tonal combination is totally adjustable with your picking attack and guitar volume pot. The amount of boost depends on the input signal level and HOT/COOL switch position. Maximum is about +10dB on lower level notes and average is about +6dB. The Simble Predriver’s special circuitry uses low noise transistor with high input impedance (over 2 Mohm) so you can boost even piezo pickups without tone loss. The output impedance is 50 Kohm so it works even in front of fuzz pedals. This pedal is powered by a 9v battery. The power consumption is very small, if you remove the input jack when not playing you can use the pedal with a 9V battery for few years!